Control means of mine roof supports



Jan. 3, 1967 F. TOWN CONTROL MEANS OF MINE ROOF SUPPORTS 2 Sheets-Sheet1 Filed Jan. 13, 1965 5240! H 5 3 9 22222 8 m 7 2 Z V07 K N 2 I g 4/ k:4 a \W D zmpwwfl A M 2 B I FKGJ.

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if 1511 11% 1mm? an. 3, W67 F. TOWN 3 CONTROL MEANS OF MINE ROOFSUPPORTS Filed Jan. 13, 1965 2 Sheets-Sheet 2 l/VVENTOR United States latent ()filice 3,2 95,8l4 Patented Jan. 3, 1967 3,295,814 CONTROL MEANSOF MINE R081 SUPPORT Frank Town, Burton .loyce, England, assignor to W.E. & F. Dolbson Limited Filed Jan. 13, 1965, Ser. No. 425,123 Claimspriority, application Great Britain, Jan. 18, 1964, 2,314/ 64 11 Claims.(Cl. Mitt-35d) This invention is for improvements in control means ofmine roof supports primarily of the kind comprising hydraulic propsinterconnected by a horizontal advancing cylinder and ram.

It has been heretofore proposed to provide for control of the differentoperations necessary with the above type of support to be instigated byoperation of electric switch means. Specifically it has been proposedfor the extending movement of a prop to cause operation of an electricswitch for instigating the next operation to be performed. However thisarrangement is such that the switch would be operated even if the roofwere so high as not to be engaged by the prop in its fully extendedcondition.

An object of the invention is to provide for operation of the switch insuch improved manner that it will be operated only when the prop isactually supporting the roof.

The invention provides a hydraulic prop having a control device forcontrolling another hydraulic device, an operating device movablymounted at an end of the prop for operating the control device, andmeans whereby relative movement between the operating device and saidend of the prop to operate the control device is eflected only when apredetermined pressure is exerted by the prop against the roof.Conveniently the prop has an operating cap slidable on the outer end ofthe ram and adapted for operating the control device consequent uponrelative sliding movement between the cap and the ram, and wherein theram, its pressure cylinder, and the cap form a diiferential piston andcylinder arrangement whereby prop-extending pressures below apredetermined pressure act in the cap to prevent said relative movementand a predetermined prop-setting pressure in the pressure cylinderovercomes the pressure in the cap to effect said relative movement andthe control device is consequently operated. Conveniently also theoperating cap is biased in projecting direction by spring means and themode termined prop pressure is sufficient to overcome the force of thisspring in addition to the fluid pressure in the cap before the controldevice is operated.

The control device may be an electric switch, or a hydraulic pilot valveand it may be operable by the operating device through the intermediaryof a cam slide movable by the operating device. Conveniently the control device is operable through a plunger and a cam slide mounted in theram, and the cam slide is operable by a spigot carried by the operatingdevice. Conveniently also the upper end of the ram is in the form of apiston, the operating device is an end cap forming a cylinder for therams upper piston, and this cylinder and ram is of less diameter thanthat of the rams lower piston and its pressure cylinder.

More specifically the ram has a central bore communicating between afluid connection and an annulus between the ram and its cylinder, a pipeis mounted in the bore to connect a second fluid connection to the ramscylinder, and the cam slide is mounted in the bore above the inlet andis formed with fluid ducts: connecting the inlet to the upper camcylinder.

The invention also provides a hydraulic prop comprising a ram andpressure cylinder therefor, first and second fluid connectionscommunicating with an annulus etween the ram and its cylinder and withthe rams cylinder respectively, a control switch mounted on the ram withan operating plunger directed to a central bore in the ram whichcommunicates with the second fluid connection, a cam slide in said boreengaging said plunger and formed with ducts for fluid from said secondfluid connection, a piston formed on the top end of the ram and throughwhich the cam slide is directed, a top end cap on the ram and forming acylinder for the rams top piston, a spring in the cap biasing itupwardly, and a spigot directed downwardly from the cap and engaging theupper end of the cam slide.

The above and other features of the invention set out in the appendedclaims are incorporated in the construction which will now be describedas a specific embodiment with reference to the accompanying drawings inwhich:

FIGURE 1 is a sectional view of a hydraulic prop according to theinvention.

FIGURE 2 is a side view thereof.

FIGURE 3 is a sectional view of a part of the hydraulic prop shown inFIG. 1 according to an. alternative embodiment of the invention.

Referring to FIGURE 1 the hydraulic prop is in this instance one of twosimilar hydraulic props which are interconnected by a horizontaladvancing cylinder and ram providing a step by step advancing roofsupport of which there is a series employed along a coal face. Thenecessary operations of extending and contracting the digerent props andin advancing the different props in a required cycle of operations isdesirably achieved automatically by each operation being accompanied byoperation of an electric switch to instigate the next operation and soon.

For this purpose in connection with the hydraulic props, each isprovided with an electric switch as indicated at 1 in FIGURE 1.

The prop is in this instance of the type comprising a cylinder 2 forminga pressure chamber 3 in which operates a piston 4 on a ram 5.

For extending the ram 5 a pipe 6 extends through the ram 5' from a lowerlocation where it communicates with the pressure chamber 3 and an upperlocation where it communicates with a chamber 7 at the position of afluid connection 8 to which there can be alternatively fitted a suitablefluid charging unit connected to a pressure fluid supply or a returnline. A second fluid connection for a return line or a charging unit, isindicated at 9 in FIGURE 2 and this is in communication with a chamber10 which is itself a communication, via a bore 11 in the ram 5 and atransverse duct 12 with the annulus 13 between the ram 5 and thecylinder 2.

For operation of the electric switch 1 there is a plunger 1.4 which isoperable, through a ball 15 by a cam slide 16 disposed in the chamber 7and having a cam face 17 engaging the ball 15.

This cam slide 16 has sealing rings 18, 19 for sealing against the fluidin the chamber 7, and the upper end of the cam slide 16 projects througha chamber 20 which houses a biasing spring 21 for biasing the cam slide16 in an upward direction.

The upper end of the ram 5 is in the form of a piston 22 which is ofless diameter than that of the piston 4.

On the upper end of the ram 5 there is fitted an end cap slide 23 whichat its lower end forms a cylinder 24 for the piston 22, there being apressure chamber 25 between the end slide 23 and the piston 22, thischamber 25 being in communication with the pressure chamber 3 throughthe pipe 6, the chamber 7, and a duct 26 in the cam slide 16 andconnecting the chamber 7 with the chamber 29 which is open to thepressure chamber 25. The end slide 23 has a central spigot 27 forengaging the cam slide 6 and mounted on this spigot there is a thrustmember 28 which is biased downwardly by resilient means 29 which in theillustration consists of Belvedere washers, but which may consist of aspring or of a rubber block or the like.

In use of the prop, the end slide 23 is normally biased in extendingdirection from the ram 5 by the resilient means 29 acting between theend slide 23 and the thrust member 28 which bears on the piston 22.

In this position of the parts the cam slide is in such a positionrelative to the ball 15 that the latter engages the lowest part of thecam 17 so that the switch 1 is not operated by the cam 17.

When the prop is next extended by applying a charging unit to theconnection 8 and a return line to connection 9, fluid pressure in thechamber 3 extends the ram 5 until the end slide 23 engages the roof(assuming the roof to be sufficiently low for this purpose). Oncontinuance of fluid pressure in the chamber 3 this is accompanied by aseparating fluid pressure being applied from the connection 8 to thecylinder 24 between the end slide 23, and the ram 5, and this inaddition to the pressure of the spring 29 prevents the ram 5 from risingrelative to the end slide 23 so that the switch 1 remains unoperated bythe cam 17.

Not until the pressure in the chamber 3 overcomes both the fluidpressure in the chamber 25 and the pressure of the spring 29 will theram 5 rise relative to the end slide 23, at which time the prop isactually supporting the roof, and it is only at this time that the camslide 16 in ram 5, in raising relative to the end slide 23 raises theswitch of the end plunger to engage the high part of the cam face 17 asheld stationary by the end slide 23, so that the cam face 17 acts on theball 15 and causes the plunger 14 to operate the switch 1.

The switch 1 is of course suitably associated with the mechanism next tobe operated and operates, for example, a solenoid operated control valvefor controlling the operation of a successive hydraulic prop in themanner hereinbefore described of a further section of a hydraulicsequence.

An important advantage of the arrangement is that the switch 1 is notonly prevented from operation when the prop engages the roof withoutactually supporting the roof but it is also prevented from operation ifthe roof happens to be so high that the prop in its fully extendedcondition does not reach the roof. In other words the switch 1 cannot beoperated to instigate the next operation under any circumstances otherthan when the prop is actually supporting the roof.

Instead of the electric switch there may be a hydraulic pilot valve 30,which, as seen in FIG. 3, will operate a hydraulically-operated controlvalve for controlling the operation of a successive hydraulic prop or afurther section of a hydraulic sequence. A valve member 32 ishydraulically actuated through inlet 34 and outlet 36 against a returnspring 38 to be actuated by plunger 14 to operate the props in themanner of switch 1 in the previous embodiment.

What I claim is:

1. A cylinder and ram assembly comprising a ram, a ram piston thereon, aram cylinder in which the ram piston is slidable, an inlet for leadingpressure fluid into said ram cylinder, a control device mounted on saidram and operable for instigating a separate operation other than that ofthe cylinder and ram assembly, operating means including an end memberaxially slidable on said ram so as to operate said control device uponrelative contraction between said end member and said ram, and pressureapplying means providing a predetermined pressure less than the loadingpressure of the ram piston and ram cylinder and disposed in separatingassociation with said end member and said ram, whereby said ram pistonand ram cylinder must be pressure loaded in excess of said predeterminedpressure before said control device is operated.

2. In a hydraulic mine roof support system comprising at least onehydraulic device, operation of which is required to be instigated byoperation of a control device, a hydraulic prop comprising (a) acylinder,

(b) a ram slidable in said cylinder,

(c) said control device being mounted on said ram,

((1) an operating device movably mounted in said ram and operativelyassociated with said control device,

(e) an end member axially slidable on the outer end of said ram, and

(f) means for causing relative movement between the operating device andthe control device for operating the latter only upon predetermined loadbeing applied to said prop.

3. A hydraulic prop according to claim 2, wherein the operating devicecomprises an operating member slidable in said ram under control of thehydraulic fluid in the prop, said member engaging a spigot biasedagainst said end member, said end member being slidable on the outer endof said ram and forming an auxiliary piston and cylinder in operativeassociation with said operating device.

4. A hydraulic prop according to claim 2, wherein said end member formsa cap axially slidable on the outer end of said ram forming an auxiliarypiston and cylinder, a fluid duct communicating between said ramcylinder and said auxiliary cylinder.

5. A hydraulic prop according to claim 2, wherein the end member and theouter end of said ram comprise an auxiliary piston and cylinder formingan auxiliary pressure chamber therebetween, the cross-sectional area ofsaid auxiliary piston and chamber being less than that of the mainpiston and pressure chamber, whereby the control device is operated onlyupon a predetermined load being applied to the prop.

6. A hydraulic prop according to claim 2, wherein the operating devicecomprises an operating member slidable in said ram under control of thehydraulic fluid in the prop, said member engaging a spigot biasedagainst said end member, said end member being slidable on the outer endof said ram and forming an auxiliary piston and cylinder in operativeassociation with said operating device.

7. A hydraulic prop according to claim 2, wherein the operating meansincludes an operating member slidable in said ram under cotnrol of thehydraulic fluid in the prop, said member engaging a spigot biasedagainst said end member, said end member being slidable on the outer endof said ram and forming an auxiliary piston and cylinder in operativeassociation with said operating device, the cross sectional area of saidauxiliary piston and chamber being less than that of the main piston andpressure chamber, whereby the control device is operated only upon apredetermined load being applied to the prop.

8. A hydraulic prop according to claim 2, wherein said end member formsa cap axially slidable on the outer end of said ram forming an auxiliarypiston and cylinder, a fluid duct communicating between said ramcylinder and said auxiliary cylinder, the cross sectional area of saidauxiliary piston and chamber being less than that of the main piston andpressure chamber, whereby the control device is operated only upon apredetermined load being applied to the prop.

9. A hydraulic prop according to claim 2, wherein the operating devicecomprises an operating member slidable in said ram under control of thehydraulic fluid in the prop, said member engaging a spigot biasedagainst said end member, said end member being slidable on the outer endof said ram and forming an auxiliary piston and cylinder in operativeassociation with said operating device and having a fluid ductcommunicating between said ram cylinder and said auxiliary cylinder, thecross sectional area of said auxiliary piston and chamber being lessthan that of the main piston and pressure chamber, whereby the controldevice is operated only upon a predetermined load being applied to theprop.

10. A hydraulic prop according to claim 2, wherein said control deviceis an electric switch.

11. A hydraulic prop according to claim 2, wherein said control deviceis a hydraulically operated pilot valve.

No references cited.

CLAUDE A. LE ROY, Primary Examiner.

1. A CYLINDER AND RAM ASSEMBLY COMPRISING A RAM, A RAM PISTON THEREON, ARAM CYLINDER IN WHICH THE RAM PISTON IS SLIDABLE, AN INLET FOR LEADINGPRESSURE FLUID INTO SAID RAM CYLINDER, A CONTROL DEVICE MOUNTED ON SAIDRAM AND OPERABLE FOR INSTIGATING A SEPARATE OPERATION OTHER THAN THAT OFTHE CYLINDER AND RAM ASSEMBLY, OPERATING MEANS INCLUDING AN END MEMBERAXIALLY SLIDABLE ON SAID RAM SO AS TO OPERATE SAID CONTROL DEVICE UPONRELATIVE CONTRACTION BETWEEN SAID END MEMBER AND SAID RAM, AND PRESSUREAPPLYING MEANS PROVIDING A PREDETERMINED PRESSURE LESS THAN THE LOADINGPRESSURE OF THE RAM PISTON AND RAM CYLINDER AND DISPOSED IN SEPARATINGASSOCIATION WITH SAID END MEMBER AND SAID RAM, WHEREBY SAID RAM PISTONAND RAM CYLINDER MUST BE PRESSURE LOADED IN EXCESS OF SAID PREDETERMINEDPRESSURE BEFORE SAID CONTROL DEVICE IS OPERATED.